1. Field of the Invention
This invention relates to a disc drive unit for driving a disc-shaped memory element, such as a flexible disc or the like, and a method and a system for controlling the disc drive unit. This invention further relates to an information processing system and other electronic equipments which include the disc drive unit.
2. Background Arts
Some of disc drive units, particularly flexible disc drive units, have no head unloading mechanism which acts to move a head away from a surface of a disc when the head is not in use for reading or writing, for the reason of reducing the size of the unit and lowering the cost of the same. The disc drive unit of this kind involves such a serious problem that the head is always held in contact state with the surface of the disc and, therefore, if the disc is continuously rotated, the disc will be worn away in relatively short time, reducing the life of the disc.
Even in the case of a disc drive unit provided with a head unloading mechanism, if a liner which is used for cleaning the surface of the disc is held in continuous contact with the surface of the disc, the disc will be worn away in relatively short time as in the case of the conventional disc drive unit without head unloading mechanism as describe above.
In order to solve these problems, it has been proposed to utilize an upstream unit which effects access to the disc in such a manner that it may control a disc drive motor to stop the rotation of the motor and consequently rotation of a flexible disc when the disc is not subjected to reading or writing operation. This proposal is effective to improve a pass durability of the disc.
According to this proposal, the rotation and stoppage of the disc drive spindle motor are carried out in response to a `motor-ON` signal outputted from the upstream unit. More particularly, this system is arranged to start the rotation of the motor by a logic `1` `motor-ON` signal and to stop the rotation of the motor by a logic `0` signal. With this arrangement, the rotation and stoppage of the motor is controlled.
The disc device of this type, however, has a drawback again as will be described hereinafter. Once the disc driving motor is stopped, a time (about 1 sec.) is required for the motor to attain its steady rotation for a reading or writing operation. Accordingly, a substantial time is needed for actuation of the disc in the conventional disc device, especially when access operation is carried out frequently. This lowers the performance of the entire system.
One of the ideas to solve these problems is to utilize a program of an upstream unit, for example, a host computer for controlling the disc rotation. In this case, the program may include functions to monitor as to whether there is a further access or not after termination of one access and stop the motor when there is no further access.
This idea, however, presents another problem that it is difficult to predict a time when the next access occurs in the program, which makes it difficult to set the timing of stoppage of the motor.
This problem might be solved by controlling the motor to stop when there is no next access within a predetermined time, for example, 5 sec. after termination of the first access.
This solution, however, again presents another problem, because all the programs to be used in the upstream units have such control functions as described above. This imposes substantial overheads for controlling the disc drive unit to the programs and lowers the performances of the programs. Thus, this proposal is not really practical.
Alternatively, an operating system may have similar control functions for the same purpose as described above. In this case, however, there remains a similar problem unsolved.